I wouldn't say that most people are stupid. I would say that for most people in most contexts the difference does not matter, if it's even evident in any way.
But there's a duty to understand a word before using it. I've quite often looked up words I don't often use before putting finger to key, and found that they didn't quite mean what I thought - so I used something else.
Although meanings do develop, we now seem to me to be allowing that to happen at a rate that creates real problems. The main one is the need for a replacement word or term to mean what the one we have undermined meant. Quite often it's marketing-related or, as mentioned above, journalism. Examples are legion.
In photography, for example, a macro lens means a lens that magnifies so much that the image on the film (sensor, now) is bigger than was the original object. It's come to mean any lens with a bit of a close-up function. That's fine and dandy, but now keen photographers need a new term for "macro".
In the 1980s, I worked on summaries of magazine articles. Desktop publishing and electronic publishing were both emerging. One means using PC-type technology for layout and so on, although the end result is normally still printed on paper. The other means that the end product is an electronic book, journal or other item, whatever the technology that produces it (although it's difficult to do electronic publishing without a computer...) Some journalists were clearly unable to "get" the difference, life got quite confusing, and the need for a new term for electronic publishing seemed a real prospect. In the end the market took off more, desktop publishing became so common-place that people stopped bothering to talk about it, and the term "electronic publishing" survived.
How long before we're having to replace terms annually with new ones because their meaning has been lost? And how do you communicate when words change that fast?
